He's been so vague that it seems like what he's talking about can't possibly be real.

But it can be real.

In 1972, the Rand Corporation released a paper written by physicist R.M. Salter that detailed an underground tube system that could send people from Los Angeles to New York City in 21 minutes.

He called it the Very High Speed Transit System, or VHST. (Not nearly as catchy a name as Hyperloop.)

Salter concluded in his paper that "the technical problems associated with the VHST development are manifold and difficult — but no scientific breakthroughs are required."

In other words, the VHST isn't just some far-out dream. It can be a reality if we address some political and construction issues.

"The general principles are fairly straightforward: electromagnetically levitated and propelled cars in an evacuated tunnel," wrote Salter.

Rand Corporation

The VHST would be a vacuum sealed tube buried underground that would zip across the country. Salter suggested making a few stops across the country because it would be more practical. It would also allow for other tube routes.

We've emailed Musk asking if his Hyperloop is similar to Salter's idea. He has not written us back. But, reading Salter's paper, it's easy to see similarities to a railgun/air hockey table style transporter.

Salter explained how it could work by saying, "The VHST's 'tubecraft' ride on, and are driven by, electromagnetic waves much as a surfboard rides the ocean's wave. The EM waves are generated by pulsed, or by oscillating, currents in electrical conductors that form the roadbed structure in the evacuated tube way. Opposing magnetic fields in the vehicle are generated means of a loop superconducting cable carrying on the order of a million amperes of current."

He says the VHST would be highly efficient. Unlike a plane, "it does not have to squander unrecoverable energy climbing to high altitudes."

The VHST would accelerate to its maximum speed, then coast for a short while, then decelerate, says Salter. It would use all its kinetic energy to accelerate, and that power would be returned when it decelerates through energy regeneration.

In 1972, the Rand Corporation said it had already examined speeds of 14,000 miles per hour. At that speed, it would take 21 minutes to go from Los Angeles to New York City.

According to Salter's research, a coast to coast VHST trip would happen faster than it takes a plane going coast to coast to get to its peak altitude.

The VHST would have to be underground. Digging the tunnels would be the biggest problem with creating the VHST. It would require political agreement and high costs to dig the actual tunnels. (90% of the cost would be building tunnels.)

There are a lot of benefits to a tunnel, though: "protection against sabotage, right of way costs, surface congestion, grade separation problems, and noise pollution go away."

Why don't we have the VHST?

Salter blamed political issues. He wrote, "History has shown that some obvious projects, such as tunneling under the English Channel proposed in the time of Napoleon, can be delayed for centuries because of political pressures."

However, he did a crude break down of the economics and he believed that a VHST could be a profitable operation. It would make money by transporting ~106 million people per year. It could also do transportation of goods to generate additional revenue.

Obviously, anything like this is a long shot.

But if it was possible in 1972, we see no reason to believe it couldn't happen in 2013.